Lubricant Compositions

ABSTRACT

A lubricant composition characterized by the Society of Automotive Engineers (“SAE”) as 75W-140 capable of meeting the American Petroleum Institute&#39;s (“API”) GL-5 performance classification requirements for use in association with a device involving metal to metal contact of moving parts comprising: (a) base-stock comprising (i) at least one relatively low viscosity polyalphaolefin, and (ii) at least one diester; (b) viscosity improver comprising (i) at least one relatively high viscosity polyalphaolefin, and (ii) polyisobutylene; and (c) a performance additive comprising at least one additive effective to improve at least one property of the lubricant and/or the performance of the equipment in which the lubricant is to be used.

FIELD OF THE INVENTION

This invention relates to lubricant compositions having utility innumerous applications, particularly in connection with gear,transmission and/or axle applications in the automotive and machineryindustries.

BACKGROUND OF THE INVENTION

An important function of lubricant compositions, and in particular gearand axle lubricant fluids, is to provide a high degree of reliabilityand durability in the service life of equipment in which it isinstalled. Lubricating oils in general, and gear and axle lubricants inparticular, frequently must satisfy a relatively large number ofperformance criteria to be commercially successful. For example, acommercially successful axle lubricant will frequently be required topossess a high degree of oxidative stability, compatibility, shearstability, corrosion avoidance or resistance, wear protection,shiftability, and extended drain. These properties represent a difficultto achieve set of performance criteria.

Gear lubricant compositions are classified by the American PetroleumInstitute (“API”) using “GL” ratings. These classifications aresubdivided into six classes. The lowest rating, API GL-1, classifiesoils used for light conditions, which consist of base oils withoutadditives. The highest rating, API GL-6, classifies oils for very heavyconditions, such as high speeds of sliding and significant shockloading, and which contain up to 10% high performance antiscuffingadditives. However, class API GL-6 is not applied any more as it isconsidered that class API GL-5 will meet most severe requirements.Lubricant compositions classified meeting API GL-5 performancerequirements are generally applied, for example, in hypoid gears havingsignificant displacement of axles.

The viscosity-temperature relationship of a lubricating composition isanother of the critical criteria to be considered when selecting alubricant for a particular application. Mineral oils commonly used as abase for single and multigraded lubricants exhibit a relatively largechange in viscosity with a change in temperature. Fluids exhibiting sucha relatively large change in viscosity with temperature have a lowviscosity index. The SAE J306 describes viscometric qualifications foraxle and gear lubricant compositions. This classification is based onthe lubricant viscosity measured at both high and low temperatures. Thehigh-temperature kinematic viscosity values are determined according toASTM D 445, with the results reported in centistokes (cSt). Thelow-temperature viscosity values are determined according to ASTM D 2983and the results are reported in centipoise (cP). These two viscosityunits are related as follows in Equation 1:

(cP/(Density,g/cm³))=cSt  (Eq. 1)

The following Table 1 summarizes high and low temperature requirementsfor qualifications of axle and gear lubricant compositions.

TABLE 1 Maximum SAE Temperature for Viscosity Viscosity of Viscosity at100° C., cSt Grade 150,000 cP, ° C. Minimum Maximum  70 W −55 4.1 —  75W −40 4.1 —  80 W −26 7.0 —  85 W −12 11.0 —  80 — 7.0 <11.0  85 — 11.0<13.5  90 — 13.5 <18.5 110 — 18.5 <24.0 140 — 24.0 <32.5 190 — 32.5<41.0 250 — 41.0 —

These Society of Automotive Engineers (“SAE”) standards are intended foruse by equipment manufacturers in defining and recommending automotivegear, axle, and manual transmission lubricants, for oil marketers inlabeling such lubricants with respect to their viscosity, and for usersin following their owner's manual recommendations.

High temperature viscosity is related to the hydrodynamic lubricationcharacteristics of the fluid. Some lubricant compositions may containhigh molecular weight polymers, known as viscosity modifiers orviscosity index improvers, which function to increase the viscosity ofthe fluids. During use, however, these polymers may shear to a lowermolecular weight, thereby resulting in a fluid with a lower viscositythan that of the new fluid. Low temperature viscosity requirements arerelated to the ability of the fluid to flow and provide adequatelubrication to critical parts under low ambient temperature conditions.

Although a substantial number of lubricant compositions have beenproduced having various needed properties where such lubricantcompositions are used, there exists a need for an additive or acombination of additives to provide an improved clean performinglubricant composition that can be used. While acceptable performance ofthe gear oil is a requirement, it is also highly desirable that theadditive or additives be low in cost and easily produced. Accordingly,there is a need in the art for a lubricant composition that meets theseindustry standards and further provides cost-effective alternatives thatmay be easily produced, and in particular lubricant compositionsclassified as SAE 75W-140 and meet GL-5 performance requirements.

SUMMARY OF THE INVENTION

Applicants have developed improved lubricant compositions, and in manyembodiments, lubricant compositions that satisfy a relatively high levelof performance for the criteria mentioned above. As used herein, theterm “lubricant composition” is used in its broadest sense to includefluid compositions that are used in applications involving metal tometal contact of parts in which at least one function of the fluid is toinhibit or reduce friction between the parts. As such, the term“lubricant composition” as used herein includes gear oils, axle oils,and the like.

In certain embodiments, the lubricant compositions of the presentinvention comprise: (a) base-stock; (b) viscosity improver; and (c) atleast one additive. Certain lubricant compositions of the presentinvention comprise: (a) base-stock comprising (i) a low viscositypolyalphaolefin (“PAO”), and (ii) at least one diester; (b) viscosityimprover comprising (i) at least one relatively high viscosity PAO-typeviscosity improver, and (ii) polyisobutylene; and (c) a performanceadditive package comprising at least one additive effective to improveat least one property of the lubricant and/or the performance of theequipment in which the lubricant is to be used. In certain embodimentsthe lubricant compositions of the present invention aremultiviscosity-grade lubricants having a SAE viscosity classification of75W-140, and meet API GL-5 performance requirements.

Applicants have found that certain embodiments of the present lubricantcompositions having an SAE viscosity classification of 75W-140 andmeeting API GL-5 performance requirements comprise:

(a) about 10-35% by weight of a low viscosity PAO;

(b) about 30-75% by weight of a high viscosity PAO;

(c) about 5-30% by weight of a diester;

(d) about 2-25% by weight of PIB;

(e) about 5-10% by weight of an additive package; and, optionally

(f) about 0.001-0.004% by weight of an antifoam agent.

Applicants have found that certain SAE 75W-140 lubricant compositions ofthe present invention meet API GL-5 performance requirements and providecost-effective lubricant compositions that exhibit improved performancein ring and pinion gears with respect to one or more, and preferablyall, of the following advantageous properties: ridging, rippling,pitting, spalling, scoring, and wear.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention is directed in one aspect to lubricantcompositions comprising: (a) base-stock; (b) viscosity improver; and (c)at least one additive. In certain embodiments the lubricant compositionis a multiviscosity-grade lubricant having a SAE viscosityclassification of 75W-140, and meets API GL-5 performance requirements.In certain embodiments, the base-stock of the present inventioncomprises: (i) a low viscosity polyalphaolefin (“PAO”); and (ii) atleast one diester. In certain embodiments, the viscosity improver of thepresent invention comprises: (i) at least one relatively high viscosityPAO-type viscosity improver; and (ii) polyisobutylene.

In certain embodiments, the performance additive package comprises atleast one additive effective to improve at least one property of theequipment in which the lubricant is to be used. The present inventionalso provides methods of making and using a fully formulated lubricant,including a fully formulated heavy duty axle fluid, and to axle, gear,transmission or drive systems containing such oils.

In general, it is contemplated that these components of the presentinvention may be present in compositions in widely varying amountsdepending on the particular needs of each application, and all suchvariations are considered to be within the broad scope of the invention.Nevertheless, applicants have found that in certain embodiments thepresent lubricant compositions comprise:

(a) about 15-65% by weight of base-stock;

(b) about 30-75% by weight of viscosity improver; and

(c) about 7-35% by weight of additive.

Applicants have found that certain lubricant compositions of the presentinvention, when used in connection with ring and pinion gears, exhibitand/or produce advantageous properties with respect to one or more, andpreferably all, of the following: ridging, rippling, pitting, spalling,scoring, and wear.

The PAOs of the present invention comprise a class of hydrocarbons thatcan be manufactured by the catalytic oligomerization (polymerization tolow-molecular-weight procedures) of linear α-olefins typically rangingfrom 1-octene to 1-dodecene, with 1-decene being a preferred material,although polymers of lower olefins such as ethylene and propylene mayalso be used, including copolymers of ethylene with higher olefins. Ingeneral, numerous particular compounds or combinations of compounds areavailable for use in connection with each of the components as describedherein.

In certain embodiments, the base-stock of the present inventioncomprises at least one relatively low viscosity PAO and at least onediester. With respect to the low viscosity PAO of the present invention,in certain embodiments the low viscosity PAO comprises a polyalphaolefinhaving a viscosity of not greater than about 12 cSt. In one embodiment,the low viscosity PAO of the present invention comprises ChevronPhillipsPAO-2 and Ineos PAO-6. Further examples of such low viscosity PAOsshould be apparent to one of ordinary skill in the art. With respect tothe diester of the present invention, in certain embodiments the diestercomprises an adipate ester. In yet other embodiments, the adipate estercomprises a decyl adipate, and even more particularly one or moreadipate esters selected from the group consisting of di-isodecyladipate, di-isodecyl azelate, and di-tridecyl adipate. While it iscontemplated that a large range of relative concentrations of suchcomponents may be present, in general, the base-stock of the presentinvention comprises in certain embodiments a low viscosity PAO:esterweight ratio of from about 7:1 to about 1:3, and preferably of fromabout 2.6:1 to about 1:1.6. In certain embodiments, the lubricantcompositions of the present invention comprise a low viscosity PAO in anamount of from about 10-35% by weight, and in yet other embodiments offrom about 12-20% by weight. In certain embodiments, the lubricantcompositions of the present invention comprise a diester in an amount offrom about 5-30% by weight, and in yet other embodiments of from about7.5-20% by weight. In certain embodiments, the viscosity improver of thepresent invention comprises at least one relatively high viscosity PAOand polyisobutylene. With respect to the high viscosity PAO of thepresent invention, in certain embodiments the high viscosity PAOcomprises a polyalphaolefin having a viscosity of greater than about 40cSt, and preferably from about 40 to about 1000 cSt. In one embodiment,the high viscosity PAO of the present invention comprises ExxonMobil orChemtura PAO-100. Further examples of such high viscosity PAOs should beapparent to one of ordinary skill in the art. With respect to thepolyisobutylenes of the present invention, in certain embodiments thepolyisobutylene comprises Ineos H-1500-SPA or Lubrizol 8404. Furtherexamples of such polyisobutylenes should be apparent to one of ordinaryskill in the art. While it is contemplated that a large range ofrelative concentrations of such components may be present, in general,the viscosity improver of the present invention comprises in certainembodiments a high viscosity PAO:polyisobutylene weight ratio of fromabout 37.5:1 to about 1.2:1, and preferably of from about 12:1 to about2.6:1. In certain embodiments, the lubricant compositions of the presentinvention comprise a high viscosity PAO in an amount of from about30-75% by weight, and in yet other embodiments of from about 40-60% byweight. In certain embodiments, the lubricant compositions of thepresent invention comprise polyisobutylene in amount of from about 2-25%by weight, and in yet other embodiments of from about 5-15% by weight.

In certain embodiments, the at least one performance additive of thepresent invention comprises a performance additive package comprising atleast one additive effective to improve at least one property of thelubricant and/or the performance of the equipment in which the lubricantis to be used. In certain embodiments, the performance additivecomprises at least one additive based on sulfur chemistry and at leastone additive based on phosphorous chemistry. A typical additive packagewould normally contain one or more of a dispersant, antioxidant,corrosion inhibitor, anti-wear agent, anti-rust agent, and extremepressure agent. In one embodiment, the additive package comprises AftonHiTec 317. Further examples of such additives should be apparent to oneof ordinary skill in the art. In certain embodiments, the additivepackage optionally comprises an antifoam agent. In certain otherembodiments, the antifoam agents comprise silicones and miscellaneousorganic compounds. In certain other embodiments, the antifoam agentcomprises lower molecular weight dimethyl siloxane. In one embodiment,the antifoam agent comprises Dow Corning DC-200/300 to 60,000 cSt.Further examples of such antifoam agents should be apparent to one ofordinary skill in the art. In certain embodiments, the lubricantcompositions of the present invention comprise an additive package in anamount of from about 5-10% by weight, and in other embodiments of fromabout 7.5-9% by weight. In certain embodiments, the lubricantcompositions of the present invention comprise an antifoam agent in anamount of from about 0.001-0.004% by weight.

The present lubricant compositions may be prepared by mixing thecomponents together at a temperature of from about 35° C. to about 95°C., preferably from about 65° C. to about 85° C. The base-stocks,viscosity improvers, and additives are placed in a suitable metal orglass vessel. Mechanical agitation is supplied to promote mixing.

Sufficient mixing time is utilized to ensure that a homogeneous productis present. The process for making the lubricant compositions of thepresent invention should be known to and appreciated by one of ordinaryskill in the art given the present disclosure. One of ordinary skill inthe art would appreciate that this method of preparation is not limitingto the invention, and that one or more components may be modified inaccordance with the teachings herein or that which is known in the art.

The lubricant compositions of the present invention preferably meet therequirements of both low-temperature and high-temperature gradelubricants, and in certain embodiments are multiviscosity-gradelubricants. Certain lubricant compositions of the present invention areclassified as SAE 75W-140 lubricants and meet the low-temperaturerequirements for SAE 75W and the high-temperature requirements for SAE140. Lubricant compositions classified as SAE 75W have a viscosity ofabout 150,000 cP at −40° C. Lubricant compositions classified as SAE 140are those having a kinematic viscosity at 100° C. of at least about 24.0cSt and less than about 32.5 cSt.

In certain embodiments the lubricant compositions of the presentinvention meet API Category GL-5 performance requirements, and in yetother embodiments meet the SAE J2360 performance standard. Certainlubricant compositions of the present invention are intended for gears.In certain embodiments, the lubricant compositions are intended forgears in automotive axles equipped with hypoid gears, operating undervarious combinations of high-speed/shock-load and low-speed/high-torqueconditions. Certain lubricant compositions of the present invention meetthe API Category GL-5 performance requirements outlined by the followingtests and acceptance criteria: (1) Standard Version of L-42; (2)Canadian Version of L-42; (3) Standard Version of test method ASTM D6121; (4) Canadian Version of test method ASTM D 6121; (5) test methodASTM D 7038 or L-33; (6) test method ASTM D 5704 or L-60; (7) testmethod ASTM D 892; and (8) test method ASTM D 130.

Based on the foregoing, one embodiment of the lubricant compositions ofthe present invention comprises: (a) a low viscosity polyalphaolefin(“PAO”); (b) a high viscosity PAO; (c) a diester; (d) polyisobutylene(“PIB”); (e) an additive; and, optionally (f) an antifoam agent; whereinthe lubricant composition is a multiviscosity-grade lubricant having aSAE viscosity classification of 75W-140 and meets API Category GL-5performance requirements. Applicants have found that in certainembodiments the present lubricant compositions comprise:

(a) about 10-35% by weight of a low viscosity PAO;

(b) about 30-75% by weight of a high viscosity PAO;

(c) about 5-30% by weight of a diester;

(d) about 2-25% by weight of PIB;

(e) about 5-10% by weight of an additive package; and, optionally

(f) about 0.001-0.004% by weight of an antifoam agent.

In certain other embodiments, the present lubricant compositioncomprises:

(a) about 12-20% by weight of a low viscosity PAO;

(b) about 40-60% by weight of a high viscosity PAO;

(c) about 7.5-20% by weight of a diester;

(d) about 5-15% by weight of PIB;

(e) about 7.5-9% by weight of an additive package; and, optionally

(f) about 0.001-0.004% by weight of an antifoam agent.

The instant invention is not necessarily limited to the foregoing. Oneof ordinary skill in the art would appreciate that this embodiment isnot limiting to the invention, and that one or more components may bemodified in accordance with the teachings herein or that which is knownin the art.

EXAMPLES

The following examples are provided for the purpose of illustrating thepresent invention, but without limiting the scope thereof.

Example Lubricant Composition 1 was prepared by mixing together thecomponents as shown in Table 2 as follows.

TABLE 2 Amount Component Composition (weight %) Base-stock Low ViscosityPAO 23 (73.9% ChevronPhillips PAO-2, 26.1% Ineos PAO-6) Base-stockDiester 14 (Cognis Synative 2970/diisodecladipate) Viscosity ImproverHigh Viscosity PAO 45 (ExxonMobil or Chemtura PAO-100) ViscosityImprover Polyisobutylene 10 (Ineos H-1500-SPA) Additive API GL-5Additive Package 8.5 (Afton HiTec 317) Additive Antifoam Additive 0.002(Dow Corning DC-200/60,000)

Performance of Lubricant Compositions in Axles Under High Speed andShock Loading: L-42 (ASTM D 7452)

The objective of this procedure is to evaluate the anti-scoringproperties of gear lubricants under high-speed and shock conditions. Theperformance of procedure lubricants is compared to that of referenceoils. A specially selected rear axle-mounting assembly and two largedynamometers serve as the procedure apparatus. A break-in is conductedat moderate speed and load at a lubricant temperature of 225° F. This isfollowed by a series of moderate accelerations and decelerations withtemperatures approaching 280° F. The final series of runs consists ofhigh-speed accelerations with rapid decelerations. This test may beperformed under two different sets of operating conditions, commonlyreferred to as “Standard” and “Canadian.” The ring and pinion gears areevaluated on a pass/fail basis. The pass/fail criteria require thatthere be less quantity of scoring on the ring and pinion gears than onthe associated pass reference oil procedure. “Scoring,” with respect toring and pinion gears, as defined by ASTM D 7450, is the rapid removalof metal from the tooth surfaces caused by the tearing out of smallcontacting particles that have welded together as a result ofmetal-to-metal contact; a scored surface is characterized by a matte ordull finish. The results of the L-42 Standard and Canadian testsperformed are reported in the following Tables 3 and 4, respectively.

TABLE 3 L-42 Standard Test Example 1 Reference % Scoring, Pinion DriveSide 0 0 Cost Side 16 22 % Scoring, Ring Drive Side 0 0 Cost Side 10 16

TABLE 4 L-42 Canadian Test Example 1 Reference % Scoring, Pinion DriveSide 0 0 Cost Side 10 22 % Scoring, Ring Drive Side 0 0 Cost Side 6 16

As can be seen from Tables 3 and 4 above, the lubricant composition inaccordance with the present invention passed both the L-42 Standard andCanadian tests by exhibiting an equal to or better (lower) score thanthe mean scoring values of the passing reference oil test results usedto calibrate the standard.

Performance of Lubricant Compositions at High Speed, Low Torque,Followed by Low Speed, High Torque: ASTM D 6121

This method is used for determining the load-carrying, wear, and extremepressure characteristics of gear lubricants in hypoid axle assembliesunder conditions of high-speed, low-torque, and low-speed, high-torqueoperation. A specially selected rear axle assembly, engine, andtransmission, and two large dynamometers serve as the procedureapparatus. The procedure axle is operated for 100 minutes at 440 axlerpm, 295° F. lubricant temperature, and 9460 lb-in of torque. The axleis then operated for 24 hours at 80 axle rpm, 275° F. lubricanttemperature, and 41,800 lb-in of torque. The ring and pinion gears areevaluated for an ASTM merit rating based on the ridging, rippling, wear,pitting/spalling, and scoring.

“Ridging,” with respect to ring and pinion gears, as defined by ASTM D7450, is the alteration of the tooth surface to give a series ofparallel raised and polished ridges running diagonally in the directionof sliding motion, either partially or completely across the toothsurfaces or gears. “Rippling,” with respect to ring and pinion gears, asdefined by ASTM D 7450, refers to an alteration of the tooth surfaceresulting to give an appearance of a more or less regular patternresembling ripples on water or fish scales. “Wear,” with respect to ringand pinion gears, as defined by ASTM D 7450, is the removal of metal,without evidence of surface fatigue or adhesive wear, resulting inpartial or complete elimination of tool or grinding marks or developmentof a discernible shoulder ridge at the bottom of the contact area nearthe root or at the toe or heel end of pinion tooth contact area(abrasive wear). “Pitting,” with respect to ring and pinion gears, asdefined by ASTM D 7450, refers to small irregular cavities in the toothsurface, resulting from the breaking out of small areas of surfacemetal. “Spalling,” with respect to ring and pinion gears, as defined byASTM D 7450, is the breaking out of flakes of irregular area of thetooth surface, a condition more extensive than pitting. “Scoring,” withrespect to ring and pinion gears, as defined by ASTM D 7450, is therapid removal of metal from the tooth surfaces caused by the tearing outof small contacting particles that have welded together as a result ofmetal-to-metal contact; a scored surface is characterized by a matte ordull finish.

This test was performed under two different sets of operatingconditions, referred to as “Standard” using “non-lubrited” hardware, and“Canadian” using “lubrited” hardware. “Lubrited,” as defined by ASTM D7450, refers to a surface coated with phosphate. The results of the ASTMD 6121 Standard, Non-Lubrited, and Canadian, Lubrited tests performedare reported in the following Tables 5 and 6, respectively.

TABLE 5 ASTM D Example 1 Minimum Requirement 6121 Test Ring Pinion RingPinion (Standard, (ASTM merit (ASTM merit (ASTM merit (ASTM meritNon-Lubrited) rating) rating) rating) rating) Ridging 10 8 8 8 Rippling10 9 8 8 Wear 8 8 5 5 Pitting/Spalling 9.9 9.9 9.3 9.3 Scoring 10 10 1010

TABLE 6 ASTM D Example 1 Minimum Requirement 6121 Test Ring Pinion RingPinion (Canadian, (ASTM merit (ASTM merit (ASTM merit (ASTM meritLubrited) rating) rating) rating) rating) Ridging 10 8 8 8 Rippling 10 98 8 Wear 8 8 5 5 Pitting/Spalling 9.9 9.9 9.3 9.3 Scoring 10 10 10 10

As can be seen from Tables 5 and 6 above, the lubricant composition inaccordance with the present invention passed both the ASTM D 6121Standard and

Canadian tests by exhibiting an equal to or better (higher) ASTM meritrating than the minimum ratings specified.

Performance of Lubricant Compositions while Subjected to WaterContamination and Elevated Temperature: ASTM D 7038

This method is used for evaluating the rust and corrosion inhibitingproperties of a gear lubricant while subjected to water contaminationand elevated temperature. An electric motor, specially selected hypoiddifferential housing assembly, cooling fan, heating lamps, and heatedstorage box serve as the procedure apparatus. The differential housingassembly is operated for 4 hours at 2,500 input rpm at 180° F. lubricanttemperature with 1 fl. oz. of distilled water mixed in the lubricant.The procedure unit is then placed in the storage box and stored for 162hours at 125° F. At the end of the procedure, the procedure parts of theassembly are rated for the presence of rust. All internal moving parts(ring, pinion, bearings, differential gears, etc.) are evaluated for afinal rust merit rating.

API Category GL-5 candidate fluids are required to have a Final RustCorrosion Merit Rating of 9.0 or greater. Example Lubricant Composition1 passed the ASTM D 7038 test by exhibiting a 9.3 Final Rust CorrosionMerit Rating.

Thermal and Oxidative Stability of Lubricant Compositions: ASTM D 5704

This method is used for determining the deterioration of lubricantsunder severe thermal and oxidative conditions. A gear case assembly, twospur gears, two copper strips, a bearing, a temperature control system,an alternator, a motor, and a regulated air supply serve as major partsof the procedure fixture. The spur gears are rotated under load at1750-rpm input for 50 hours. The lubricant temperature is maintained at325° F. Airflow through the lubricant is controlled at 22.1 mg/min forthe procedure's duration. The physical and chemical properties of theoil and deposits on the gears are evaluated at the end of the procedure.The large and small gears are evaluated for carbon/varnish and sludge.The used oil is evaluated for any increase in viscosity, pentaneinsolubles, and toluene insolubles. The results of the ASTM D 5470 testperformed are reported in Table 7 as follows.

TABLE 7 ASTM D 5704 Test Example 1 API GL-5 Requirement ViscosityIncrease, % 16 ≦100 Pentane Insolubles, wt. % 0.5 ≦3.0 TolueneInsolubles, wt. % 0.7 ≦2.0 Carbon/Varnish 7.8 ≦7.5 Sludge 9.4 ≦9.4

As can be seen from Table 7 above, the lubricant composition inaccordance with the present invention passed the ASTM D 5704 test byexhibiting % viscosity increase, weight % pentane and tolueneinsolubles, and carbon/varnish and sludge values as required by the APIGL-5 acceptance criteria.

Foaming Properties of Lubricant Compositions: ASTM D 892

This method is used for determining the foaming properties of a gearlubricant at 24° C. and 93.5° C. Foaming is undesirable since foamcannot adequately protect gear or bearing surfaces in an automotivedrive train. Oil is placed in a large glass cylinder and air is blown infrom the bottom using a porous stone. The amount of any resulting foamis measured visibly. The used oil is evaluated in three sequences fortendency/stability. The results of the ASTM D 892 test performed arereported in Table 8 as follows.

TABLE 8 ASTM D 892 Test Example 1 API GL-5 Requirement Sequence 1, ml(tendency/stability) 0/0 ≦20 Sequence 2, ml (tendency/stability) 0/0 ≦50Sequence 3, ml (tendency/stability) 0/0 ≦20

As can be seen from Table 8 above, the lubricant composition inaccordance with the present invention passed the ASTM D 892 test byexhibiting tendency/stability foaming properties as required by the APIGL-5 acceptance criteria.

Copper Corrosion Properties of Lubricant Compositions: ASTM D 130

This method is used for determining a lubricant's compatibility with“yellow metal” or copper. Attack on copper, brass, or bronze would beundesirable for those parts located in an automotive drive train. Asmall metal strip is placed in a sample of test oil. The oil is heatedin a block or oven for 3 hours at 210° F. The strip is given an ASTMrating for color change in comparison to a set of known standards. APICategory GL-5 candidate fluids are required to have an ASTM rating ofless than or equal to 3. Example Lubricant Composition 1 passed the ASTMD 130 test by exhibiting a 2e ASTM rating.

1. A lubricant composition for use in association with a deviceinvolving metal to metal contact of moving parts comprising: (a)base-stock comprising (i) at least one relatively low viscositypolyalphaolefin, and (ii) at least one diester; (b) viscosity improvercomprising (i) at least one relatively high viscosity polyalphaolefin,and (ii) polyisobutylene; and (c) a performance additive comprising atleast one additive effective to improve at least one property of thelubricant and/or the performance of the equipment in which the lubricantis to be used; wherein said lubricant composition meets the AmericanPetroleum Institute's GL-5 performance classification requirements. 2.The lubricant composition of claim 1 wherein said lubricant compositionis a multiviscosity-grade lubricant having a viscosity of about 150,000cP at −40° C. and a kinematic viscosity at 100° C. of at least about24.0 cSt and less than about 32.5 cSt.
 3. The lubricant composition ofclaim 2 wherein said base-stock comprises at least one polyalphaolefinhaving a viscosity of not greater than about 12 centistokes (cSt). 4.The lubricant composition of claim 2 wherein said viscosity improvercomprises a polyalphaolefin having a viscosity of greater than about 40centistokes (cSt).
 5. The lubricant composition of claim 2 comprising:(a) about 15-65% by weight of base-stock; (b) about 30-75% by weight ofviscosity improver; and (c) about 7-35% by weight of additive.
 6. Alubricant composition for use in association with a device involvingmetal to metal contact of moving parts comprising: (a) about 10-35% byweight of a low viscosity polyalphaolefin; (b) about 30-75% by weight ofa high viscosity polyalphaolefin; (c) about 5-30% by weight of adiester; (d) about 2-25% by weight of polyisobutylene; (e) about 5-10%by weight of an additive package; and, optionally (f) about 0.001-0.004%by weight of an antifoam agent; wherein said lubricant composition meetsthe American Petroleum Institute's GL-5 performance classificationrequirements.
 7. The lubricant composition of claim 8 wherein saidlubricant composition is a multiviscosity-grade lubricant having aviscosity of about 150,000 cP at −40° C. and a kinematic viscosity at100° C. of at least about 24.0 cSt and less than about 32.5 cSt.
 8. Thelubricant composition of claim 7 wherein said low viscositypolyalphaolefin has a viscosity of not greater than about 12 centistokes(cSt).
 9. The lubricant composition of claim 7 wherein said highviscosity polyalphaolefin has a viscosity of greater than about 40centistokes (cSt).
 10. The lubricant composition of claim 7 wherein saidlubricant composition comprises: (a) about 12-20% by weight of a lowviscosity polyalphaolefin; (b) about 40-60% by weight of a highviscosity polyalphaolefin; (c) about 7.5-20% by weight of a diester; (d)about 5-15% by weight of polyisobutylene; (e) about 7.5-9% by weight ofan additive package; and, optionally (f) about 0.001-0.004% by weight ofan antifoam agent.